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Editor's Note: Although the changes in ETA model of NCEP (USA) may not be directly related to the Asian meteorology, some meteorologists, especially in the NWP groups of the meteorological services in Asian countries, showed great interests on this news. So the editor decided to put it in this issue.
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Changes to the Operational Early and Meso ETA Models
[From National Technical Information Message (NTIM) 97-10]
National Weather Service Headquarters, Washington DC
Feb. 18 1997
At 1200 UTC 18 Feb. 1997 a series of changes to the operational early
(48KM/38LEV) and meso (29KM/50LEV) ETA models were implemented. A
brief description of each change follows:
MODEL CHANGES
- Addition of a form-drag scheme
- Implementation of a more efficient and accurate positive
definite advection scheme for moisture and cloud
- Eccentric (rather than circular) orbit around the sun
- Corrected atmospheric ozone distribution
- Effect of aerosols on net shortwave radiation added
- Reduced albedo over snoW
- Model radiation impacted by cloud in each individual model
layer, rather than through 3 deep layers
- Improved computation of cloud fraction
- Improved input fields of vegetation greenness fraction anD
initial soil moisture
- Enhanced bare soil evaporation
- Corrections to physical processes related to melting snow
- Increased the background level of turbulent mixing
POST-PROCESSOR CODE AND OUTPUT CHANGES
- Implementation of a more efficient version of the ETA model
post-processing code
- The following grids will be directly output by the early ETA
model post-processor (complementing the existing grids) at 6-h
forecast intervals:
- AWIPS grid 211 (80 KM Lambert conformal over CONUS)
- AWIPS grid 214 (48 KM polar stereographic over ALASKA)
- The following grids will be directly output by the early ETA
model post-processor at 3-h forecast intervals:
- AWIPS grid 212 (40 KM Lambert conformal over CONUS)
- ETA model computational grid on pressure levels
- ETA model computational grid on model levels
These additional fields will be accessible via anonymous FTP on the
NIC server (NIC.FB4.NOAA.GOV or 140.90.50.22). The content and
timeliness of the current ETA model products on the OSO server
remains unchanged. The additional grids described above will be
available on the OSO server in the near future.
A previously advertised change of GRIB file identifiers for ETA
boundary layer fields (GRIB PDS OCTETS 9-12) is not part of this
implementation due to delays in users software conversion. These
changes will occur at a later date.
Above changes based on data provided by Eric Rogers at
Environmental Modeling Center - NCEP. For specific questions -
contact him at (301) 763-8161 FAX (301) 763-8545 - also at E-mail address -
eric.roger@noaa.gov.